CN104284317B - Report is on the method for the feedback information of the independent subband of wireless channel, base station, movement station - Google Patents

Abstract

In order to report the feedback information on wireless channel, movement station determines whether to meet predefined condition.In response to determining to meet predefined condition, the feedback information of independent one in a plurality of subbands on wireless channel is included in the first report of base station to be sent to.In response to determining to be unsatisfactory for predefined condition, it will include on the aggregated feedback information of a plurality of subbands in the second report of base station to be sent to.

Description

Method for reporting feedback information on individual subbands of wireless channel, base station, mobile mobile station

This application is a divisional application of an invention patent application with an application date of June 25, 2009, an application number of 200980124006.7, and an invention title of "Including Feedback Information About Individual Subbands of Wireless Channels".

Background technique

Various wireless access technologies have been proposed or implemented to enable mobile stations to perform communications with other mobile stations or with wired terminals coupled to a wired network. Examples of radio access technologies include GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) technologies defined by the Third Generation Partnership Project (3GPP); and CDMA2000 (Code Division Multiple Access 2000) technologies defined by 3GPP2 .

As part of the continued evolution of wireless access technologies to improve spectral efficiency, improve services, reduce costs, etc., new standards have been proposed. One such new standard is the Long Term Evolution (LTE) standard from 3GPP, which seeks to enhance UMTS wireless networks.

In some cases, it may be desirable to provide feedback information about the wireless channel, where the feedback information may be sent from a mobile station to a base station. This feedback information may include information that allows the base station to apply selected modulation and coding to data transmitted from the base station to the mobile station. Additionally, the feedback information may include an indication of wireless channel quality.

According to the conventional LTE standard, a radio channel for communicating data is divided into subbands (also referred to as bands). A subset of subbands can be identified as optimal subbands available for communication of data between the base station and the mobile station. The legacy LTE standard supports various information feedback modes, but they may not be optimal. For example, the PUSCH (Physical Uplink Shared Channel) reporting mode 2-2 defined by the LTE standard does not consider providing feedback information about the radio channel for selected subbands on an individual subband basis, which reduces flexibility and degrades radio channel performance. data communication quality.

Contents of the invention

In general, according to a preferred embodiment, in order to report feedback information on a wireless channel, a mobile station determines whether a predefined condition is fulfilled. If satisfied, feedback information on a single one of plural subbands of the wireless channel is included in a report to be sent to the base station. However, in response to determining that the predefined condition is not met, the aggregated feedback information on the plurality of subbands is included in another report to be sent to the base station.

Other or alternative features will become apparent from the following description, drawings and claims.

Description of drawings

Figure 1 is a block diagram comprising an exemplary arrangement of a wireless communication network incorporating a preferred embodiment of the present invention;

Figures 2 and 3 illustrate different reports that may be communicated from a mobile station to a base station to provide feedback information about a wireless channel in accordance with a preferred embodiment; and

4-8 are flowcharts of processes for communicating and/or using feedback information about a wireless channel according to a preferred embodiment.

detailed description

In the following description, numerous details are set forth to provide an understanding of some embodiments. However, it will be understood by those skilled in the art that some embodiments may be practiced without these details and that many variations or modifications may be possible from the described embodiments.

According to some preferred embodiments, there is provided a technique or mechanism for reporting feedback information on a wireless channel, wherein the feedback information on individual subbands can be provided to a base station. As used herein, the term "wireless channel" refers to a collection of resources that can be used by wireless nodes (including mobile stations and base stations) to communicate wirelessly with each other. The resources include subcarriers of different frequencies. Furthermore, resources may include different slots or different precoding vectors. In one embodiment, the wireless channel may be implemented according to an Orthogonal Frequency Division Multiplexing (OFDM) arrangement in which the resources of the wireless channel may be organized by time slots (along time dimension) and combinations of subcarriers of different frequencies (along the frequency dimension).

In an OFDM arrangement, a subband (also referred to as a "band") may include a number of subcarriers along the frequency dimension and all OFDM symbols (slots) along the time dimension. A wireless channel can thus be divided into subbands. More generally, a "subband" refers to some predefined portion of a wireless channel, which may have multiple such predefined portions for communicating data between a mobile station and a base station.

Feedback information that may be provided from the mobile station to the base station includes feedback information to recommend modulation and coding. In this case, the feedback information includes an index (or other type of indicator) enabling selection of modulation and coding to be applied to signaling on the downlink. In some examples, the index includes a precoding matrix index (PMI) that can be used to apply precoding at the base station.

Another example of feedback information that can be sent from a mobile station to a base station includes a channel quality indicator (CQI), which is an indication of the quality of a wireless channel.

According to some embodiments, the type of feedback information reported from the mobile station back to the base station depends on whether a predefined condition is fulfilled. In some embodiments, the predefined condition is an indication of whether the mobile station is a slow moving (or stationary) mobile station or a fast moving (high speed) mobile station. For slow moving mobile stations, it is likely that the parameters of the feedback information do not change for several reporting periods, so that it is redundant to report the same parameters in corresponding reporting periods. For a slowly moving mobile station, different feedback information may be sent in different reporting periods instead of repeatedly sending the same parameters in consecutive reporting periods. In other words, the reporting periods of different types of feedback information for different users may be set to different values.

In some reporting modes, the feedback information (including CQI and/or PMI) sent from the mobile station to the base station is aggregated feedback information reflecting properties of multiple subbands. The aggregated feedback information may be an average or some other aggregated information reflecting properties of multiple subbands.

However, according to some preferred embodiments, instead of sending aggregated feedback information, individual feedback information for individual subbands (referred to as "incremental feedback reports") may be reported when a predefined condition is detected. Thus, instead of reporting aggregated CQI for multiple subbands, for example, individual CQIs for individual subbands may be reported. Similarly, individual PMIs may be reported for individual subbands instead of an aggregated PMI based on aggregated attributes of multiple subbands.

From among the set of subbands for a wireless channel, a subset of the subbands can be identified as a preferred or "best" subband for the wireless channel. For example, M (M>1) subbands may be identified. These M subbands may be used to communicate traffic data or higher layer signaling information between the base station and the mobile station.

Figure 1 illustrates an exemplary wireless network in which some embodiments of the present invention may be provided. The wireless network comprises a base station 100 comprising an antenna array or other components (multi-beam antennas) 102 for transmitting wireless signals along a plurality of paths 104, 106 (spatial beams) in corresponding cell sectors 108 . In various implementations, antenna array 102 may include only a single antenna for transmitting wireless signals along one path.

A cell sector is a subdivision of a cell of a cellular network. Although only two paths 104 and 106 are depicted in Figure 1, it is noted that in other embodiments more than two paths (or only one path) may be provided in a cell sector. In alternative embodiments, note that multiple beams may be provided in a cell instead of multiple beams in a cell sector. As used herein, the term "cell segment" may refer to a cell sector or cell.

Although only one base station is depicted in Figure 1, it is noted that a wireless network will typically include multiple base stations. In some embodiments, the wireless network is an LTE wireless network. In alternative embodiments, other types of wireless networks may be employed. Note that reference to an "LTE wireless network" refers to a wireless network conforming to the requirements of the LTE standard developed by 3GPP as the standard is modified or evolved over time, as well as subsequent standards evolved from LTE. Furthermore, even though LTE wireless networks are mentioned in the ensuing discussion, it is noted that the techniques according to the preferred embodiments can also be applied to non-LTE, OFDM based wireless networks.

In an LTE wireless network, a base station 100 includes an enhanced node B ("eNode B") that includes a base station transceiver that includes an antenna array 102 . The base station 100 may also include a radio network controller cooperating with eNodeBs. The radio network controller and/or eNode B may perform one or more of the following tasks: radio resource management, mobility management for managing mobility of mobile stations, routing of traffic, etc. Note that one radio network controller may have access to multiple eNode Bs, or alternatively an eNode B may be accessed by more than one radio access controller.

More generally, the term "base station" may refer to a cellular network base station, an access point used in any type of wireless network, or any type of wireless transmitter that communicates with mobile stations.

As depicted in FIG. 1 , the base station 100 includes one or more central processing units (CPUs) 122 connected to storage devices 124 . Furthermore, the base station 100 includes software 126 operable on the CPU(s) 122 to perform the tasks of the base station 100, including the tasks of implementing support for SDMA in an LTE wireless network according to a preferred embodiment.

The mobile station 110 of FIG. 1 also includes one or more CPUs 130 connected to a storage device 132 . The mobile station 110 also includes software 134 capable of running on the CPU(s) 130 to perform the tasks of the mobile station 110 .

The base station 100 is connected to a serving and/or packet data network (PDN) gateway 112, which terminates towards the user plane interface of the eNode B and takes responsibility for packet routing and transmission towards an external network 114, which It may be a packet data network such as the Internet or another type of network.

For example purposes, the arrangement depicted in Figure 1 is provided. In other embodiments, other wireless network arrangements are used.

As mentioned above, according to some embodiments, incremental reporting of feedback information including CQI and PMI may be performed. In one embodiment, reporting of such feedback information may be in a Physical Uplink Shared Channel (PUSCH). However, in other embodiments, the feedback information may be provided in other types of channels or messages sent from the mobile station to the base station, such as the Physical Uplink Control Channel (PUCCH). In general, feedback information may be said to be sent in a report, where a "report" may include a message, fields of a message, multiple messages, and so on.

According to some implementations, the two modes of operation defined by the LTE standard may employ incremental feedback reporting according to the preferred embodiment. These two modes of operation include LTE PUSCH reporting mode 2-0 and mode 2-2. PUSCH reporting mode 2-0 defined by LTE is used for single-input multiple-output (SIMO) communication, space-frequency block coding (SFBC) communication, or open-loop spatial multiplexing (SM) communication. In this reporting mode, precoding information is not included in the feedback.

Mode 202 according to LTE refers to closed loop MIMO (Multiple Input Multiple Output) communication, where closed loop MIMO uses feedback information to apply coding. For example, based on feedback information (in the form of PMI) from the mobile station, the base station applies the selected precoding.

Although LTE Mode 2-0 and Mode 2-2 are referred to in this discussion, it is noted that incremental feedback reporting according to the preferred embodiment can also be applied to other types of wireless communications.

Incremental reporting of individual CQI for enhanced LTE PUSCH reporting mode 2-0 is depicted in FIG. 2 . Four reports for four consecutive reporting intervals (1, 2, 3, 4) are depicted in Fig. 2 . In one embodiment, these four reports are carried by PUSCH from the mobile station to the base station. The report sent from the mobile station to the base station includes a bitmap field 202 (which contains the bitmap), a subband CQI information field 204 which optionally contains aggregated CQI or individual CQI, and a wideband CQI information field 206 which contains the wideband CQI. The bitmap identifies the M preferred subbands. The bitmap includes a plurality of bits corresponding to the corresponding subbands. Setting a corresponding one bit means that the corresponding subband is identified as preferred. In other implementations, other types of data structures may be used to indicate which subbands are preferred.

The subband CQI information field 204 may include an aggregate CQI for the M subbands identified by the bitmap or an individual CQI for one of the M subbands. In reporting interval 1, as shown in FIG. 2, the subband CQI information field 204 contains the aggregated CQI over the M subbands. The wideband CQI information field 206 contains the aggregated CQI over the entire wireless channel (including all subbands).

Assuming that the above predefined condition is not satisfied in reporting interval 1, the CQI conveyed in the subband CQI information field 204 is thus the aggregated CQI over the M subbands. In some embodiments, the predefined conditions are based on the content of the bitmap. The predefined condition is met if the current bitmap is the same as the previous bitmap (in the previous reporting interval). However, the predefined condition is not satisfied if the current bitmap is different from the previous bitmap in the previous reporting interval. Maintaining the same bitmap in consecutive reporting intervals is an indication that the mobile station is a slow moving or stationary mobile station.

In the example of FIG. 2, it is assumed that in each of reporting intervals 2-4, the bitmap remains the same as the bitmap reported in time interval 1 . In reporting interval 2, the subband CQI information field 204 includes an individual CQI for the first individual subband among the M subbands. Similarly, in reporting intervals 3 and 4, the subband CQI information field 204 of the respective reports contains separate CQIs for the corresponding second and third subbands from the M subbands. Therefore, when the bitmap does not change, individual CQIs can be reported instead of aggregated CQIs.

Although FIG. 2 shows an embodiment in which only one individual CQI for a corresponding individual field may be included in each report, note that in alternative embodiments multiple individual CQIs for a corresponding subband may be included in one report.

Figure 3 shows reports sent in four different reporting intervals (1, 2, 3, 4) for Enhanced LTE PUSCH reporting mode 2-2. In mode 2-2, in addition to CQI information, PMI information is also provided (because closed-loop MIMO is used). Also, in Mode 2-2, it is assumed that there are two transmission codewords, so that CQI information for the two transmission codewords is reported separately. In each report shown in FIG. 3, bitmap field 302 contains a bitmap, first subband CQI field 304 contains subband CQI information for the first transmitted codeword, wideband CQI field 306 contains wideband CQI, second The subband CQI information field 308 contains subband CQI information for the second transmit codeword, and the PMI information field 310 contains PMI information. In reporting interval 1 of FIG. 3, it is assumed that the current bitmap is different from the previous bitmap (in the previous reporting interval). As a result, the subband CQI provided in subband CQI information fields 304 and 308 and the PMI information in PMI information field 310 are the aggregate CQI and PMI for the M subbands identified by the bitmap in field 302, respectively.

However, in reporting intervals 2-4, it is assumed that the bitmap remains the same as in reporting interval 1, in which case the subband CQI information fields 304 and 308 may include individual CQIs for the corresponding transmit codewords , where different individual CQIs for different subbands are reported in consecutive reporting intervals.

Also, the PMI information contained in the PMI information field 310 includes individual PMIs for individual subbands in reporting intervals 2-4, wherein different individual PMIs for corresponding subbands are reported in consecutive reporting intervals 2-4.

4 and 5 depict the operation of a mobile station and a base station, respectively, for enhanced PUSCH reporting Mode 2-0 operation. During the current reporting interval, the mobile station determines (at 402) whether the current bitmap is the same as the previous bitmap. If not, the CQI information (FIG. 2) reported (at 404) in the subband CQI information field 204 is the aggregated CQI over the M subbands. However, if the current bitmap is the same as the previous bitmap, the CQI information reported (at 406) in the subband CQI information field 204 is the individual CQI for the corresponding individual subband.

As shown in Figure 5, the base station determines (at 502) whether the current bitmap is the same as the previous bitmap. If not, the base station uses (at 504) the previously received aggregated CQI. However, if the current bitmap is the same as the previous bitmap, the base station uses (at 506) the individual CQI for the selected subband for downlink data transmission from the base station to the mobile station.

6 and 7 depict enhanced PUSCH reporting Mode 2-2 operation for a mobile station and a base station, respectively. In FIG. 6, the mobile station determines (at 602) whether the current bitmap is the same as the previous bitmap. If not, the aggregated CQI and PMI information for the M subbands is provided (at 604) for the subband CQI information fields 304 and 308 and the PMI information field 310 (FIG. 3) of the feedback report. However, if the current bitmap is the same as the previous bitmap, a separate CQI and a separate PMI are provided (at 606) in corresponding fields 304, 308 and 310 as depicted in time intervals 2, 3 or 4 of FIG. 3 .

Figure 7 illustrates the operation of the base station. The base station determines (at 702) whether the current bitmap is the same as the previous bitmap. If not, the base station uses (at 704) the aggregated CQI and aggregated PMI for communicating downlink information to the mobile station. On the other hand, if the current bitmap is the same as the previous bitmap, the base station uses (at 706) the corresponding individual CQI and individual PMI for the selected subband used by the base station to communicate data to the mobile station.

In the previous discussion, it was assumed that a mobile station made a decision on whether to perform incremental reporting of individual CQI and/or PMI for a subband. In an alternative embodiment, the base station makes the decision as to whether the mobile station should send separate feedback information for separate subbands.

For example, as shown in Figure 8, the base station may decide that it wishes to receive separate feedback information from the mobile station on separate subbands. In response to making such a determination, the base station sends (at 802) a control indication to the mobile station. The control indication may be in the form of higher layer control signaling, such as radio resource control (RRC) signaling. The control indication may be sent in response to the base station determining that a predefined condition is met, such as a bitmap that has not changed in successive reporting intervals.

In response to the control indication, the mobile station sends (at 804) individual feedback information (individual CQI(s) and/or individual PMI(s)) for the individual subband(s) to the base station . Individual feedback information may be communicated in a physical uplink control channel (PUCCH) or other channels.

However, if the base station determines that the predefined condition is not satisfied, the base station sends another control instruction to make the mobile station send aggregated feedback information for the plurality of subbands.

The tasks of FIGS. 4-8 may be performed by software in the mobile station 110 or the base station 100 of FIG. 1 . Instructions for such software run on a processor (eg, CPUs 130 and 122 in FIG. 1). Processors include microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. A "processor" may refer to a single component or a plurality of components (eg, one or more CPUs).

The data and instructions (of the software) are stored in respective storage devices embodied as one or more computer-readable or computer-usable storage media. Storage media include various forms of memory including semiconductor memory devices such as dynamic or static random access memory (DRAM or SRAM), erasable and programmable read-only memory (EPROM), electrically erasable and programmable read-only memory (EEPROM) and flash memory); magnetic disks (such as fixed hard disks, floppy disks, and removable disks); or magnetic media including magnetic tape; and optical media (such as compact disks (CDs) or digital video disks (DVDs).

In the foregoing description, numerous details are set forth to provide an understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details. While this invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will recognize many modifications and changes thereto. The appended claims are intended to cover such modifications and changes as fall within the true spirit and scope of the invention.

Claims (20)

1. A method of reporting feedback information about a wireless channel, comprising: determining by the mobile station whether the preferred subband of the wireless channel has not changed; In response to determining that the preferred subband of the wireless channel has not changed, including feedback information about a single one of the plurality of subbands of the wireless channel in the first report to be sent to the base station; and In response to determining a preferred subband change for the wireless channel, aggregated feedback information on the plurality of subbands is included in a second report to be sent to the base station. 2. The method of claim 1, wherein the aggregated feedback information comprises an average of properties of a plurality of subbands. 3. The method of claim 1, wherein determining whether a preferred subband of the wireless channel has not changed comprises determining whether a data structure identifying the preferred subband has not changed. 4. The method of claim 3, wherein determining whether a data structure identifying a preferred subband has not changed comprises determining whether a bitmap identifying a preferred subband has not changed. 5. The method of claim 1, further comprising: After sending the first report, if the preferred subband of the wireless channel has not changed, further feedback information on the second individual one of the plurality of subbands is included in a third report to be sent to the base station. 6. The method of claim 1, further comprising: Further feedback information regarding a second individual one of the plurality of subbands is included in the first report. 7. The method of claim 1, further comprising: Data communication using one or more of a plurality of subbands less than all available subbands of the wireless channel is performed by the mobile station. 8. The method of claim 1, wherein data communication is performed according to a closed-loop multiple-input multiple-output (MIMO) mode of operation. 9. The method of claim 8, wherein the mobile station transmits a plurality of codewords, and wherein the feedback information included in the first report is for a first codeword of the plurality of codewords, and wherein the first The report also includes feedback information for individual subbands of another codeword of the plurality of codewords. 10. The method of claim 1, wherein the feedback information in the first report for an individual subband comprises at least one of: Precoding Matrix Index (PMI); and Channel Quality Indicator (CQI). 11. A base station, comprising: an interface for wirelessly communicating with the mobile station over a wireless channel; and processor, configured to: determining whether the preferred subband of the wireless channel has not changed; using individual feedback information for individual subbands of the plurality of subbands of the wireless channel in response to determining that the preferred subband of the wireless channel has not changed; and Aggregated feedback information for the plurality of subbands is used in response to determining a preferred subband change for the wireless channel. 12. The base station of claim 11, wherein the aggregated feedback information comprises an average of properties of a plurality of subbands. 13. The base station according to claim 11, wherein the individual feedback information or the aggregated feedback information is used for downlink signaling and traffic data to be transmitted to the mobile station. 14. The base station according to claim 11, wherein the individual feedback information comprises at least one of the following: an individual channel quality indicator (CQI); and Individual Precoding Matrix Index (PMI). 15. The base station of claim 11 , wherein to determine whether the preferred subband of the wireless channel has not changed, the processor is further configured to: It is determined whether a bitmap for a current reporting interval has not changed from a bitmap for a previous reporting interval, where the bitmap identifies a plurality of subbands. 16. A mobile station comprising: an interface for wirelessly communicating with the base station via a wireless channel; and processor, configured to: determining whether the preferred subband of the wireless channel has not changed; In response to determining that the preferred subband of the wireless channel has not changed, including individual feedback information for a single one of the plurality of subbands of the wireless channel in the first report to be sent to the base station; and In response to determining a preferred subband change for the wireless channel, aggregated feedback information on the plurality of subbands is included in a second report to be sent to the base station. 17. The mobile station of claim 16, wherein the aggregated feedback information comprises an average of properties of a plurality of subbands. 18. The mobile station of claim 16, wherein the first report includes a bitmap identifying a plurality of subbands as preferred subbands. 19. The mobile station of claim 16, wherein the individual feedback information includes at least one of: an individual channel quality indicator (CQI); and Individual Precoding Matrix Index (PMI). 20. The mobile station of claim 16, wherein to determine whether the preferred subband of the wireless channel has not changed, the processor is further configured to: Determines whether the bitmap identifying multiple subbands remains the same for consecutive reporting intervals.